The invention relates to data storage of a distributed storage subsystems.
Enterprises often have storage subsystems that use large arrays of physical storage devices to provide shared data storage for host devices. Typically, the host devices are isolated so that they are unaware of the complete physical layout of data storage of the storage subsystem. Instead, the host devices know the logical layout of data storage.
By isolating host devices from the physical layout of the storage subsystem, host applications become more portable. The host applications can execute on host devices using storage subsystems having different physical layouts. But, such host devices are also unaware of the workloads of the individual physical storage devices.
Since the host devices do not know the workloads of physical storage devices, they cannot change their storage usage patterns to compensate for overloading particular physical storage devices. Overloading a physical storage device can cause the device""s physical drives to operate slowly. Slow physical drives lead to long access times and degraded performance of the host applications that use the storage device.
Various embodiments provide apparatus and methods for rolling back a configuration of a storage subsystem to an earlier configuration. Rolling back configurations can help system managers who wish to experiment with different storage configurations, e.g., to accommodate different usage patterns of the storage subsystem. A system manager may tentatively reconfigure the storage subsystem and still be able to roll back the subsystem to an earlier configuration if the new configuration does not improve performance.
In one aspect, the invention provides a method of reconfiguring a storage subsystem. The method includes performing a first ordered sequence of reconfigurations of physical volumes of the storage subsystem. The method includes then performing a portion of the reconfigurations in a second ordered sequence in response to receiving a rollback request. The order of the second sequence is reversed with respect to the order of the first sequence.
In another aspect, the invention provides a method of reconfiguring a storage subsystem. The method includes performing a series of swaps of physical storage volumes of the subsystem and recording each swap in a list in response to performing the swap. The method also includes reading a portion of the list and undoing a portion of the swaps read from the list.
In another aspect, the invention provides a data storage device storing a computer executable program of instructions for reconfiguring a storage subsystem. The instructions cause the computer to perform a series of swaps of physical storage volumes. The swaps have been previously performed in a reversed order.
In another aspect, the invention provides a data storage device storing a computer readable object. The object includes a list identifying swaps performed on pairs of physical storage volumes of a storage subsystem.
In another aspect, the invention provides an apparatus. The apparatus includes a storage subsystem having a plurality of physical storage volumes and a computer capable of reconfiguring the storage subsystem. The computer can reconfigure the system by swapping storage volumes and can roll back the storage subsystem to an earlier configuration.